-bash: syntax error... with ps -p <pid-of-irb-process>

pdf page 19, chapter 3. Leaving irb running and in new terminal window or new tab typing
$ ps -p <pid-of-irb-process>
doesn’t show the irb Process.pid but:
-bash: syntax error near unexpected token `newline'
It’s a minor thing and I’m going to just continue reading but I’ve built up some momentum, grooving on this unix stuff and wondering what I’m doing wrong. Hoping that it’s an isolated problem for me. Anyone have any thoughts? Thanks in advance…
—Ben

Benjamin,

You need to replace pid-of-irb-process with the actual process ID for this to work. It’s just a placeholder.

-Mathias

That’s it! Sort of obvious now that you point it out. Thanks!